1. Field of the Invention
The present invention relates to a radar device for a mobile body and particularly to a radar device for a mobile body having a sensor body which transmits and receives electromagnetic waves such as millimeter waves and microwaves. The radar device for a mobile body according to the present invention can be suitably used, for example, as a radar device mounted on a vehicle and using millimeter waves.
2. Description of the Related Art
On-vehicle radar devices include laser radar devices using laser light, and electromagnetic wave radar devices using electromagnetic waves such as millimeter waves and microwaves. Among them, the electromagnetic wave radar devices attract much attention these days, because the electromagnetic wave radar devices are less susceptible to rain, snow, fog and other environmental factors than the laser radar devices, and are contributable to antenna miniaturization owing to superior linearity and directivity of electromagnetic waves with short wavelengths such as millimeter waves.
The on-vehicle electromagnetic wave radar device is used with a main purpose of detecting an obstacle ahead of the vehicle or measuring a distance between a preceding vehicle and the vehicle by transmitting millimeter waves or the like and receiving the millimeter waves or the like which have impinged on and been reflected by an object. In order to perform its functions such as detecting a preceding vehicle, the on-vehicle radar device is installed around a center of a vehicle front and particularly in a space between a front grill and a radiator. (See Japanese Unexamined Patent Publication (KOKAI) No. 2003-202369, for instance.)
Depending on vehicles, however, the abovementioned space for installing an on-vehicle radar device is sometimes restricted by a front design, the sizes and shapes of structures such as a radiator placed under a hood, a vehicular shock absorbing structure and the like. Accordingly, the on-vehicle radar device sometimes cannot be installed at a functionally most suitable site.